In a previous era, the microscope was considered a breakthrough invention that provided access to a miniature world once beyond our ability to explore. Today's technology has built upon this foundation to continue to erode the dimensional limits on what we can see, manipulate, build, and develop. For example, the nanometer is a common unit of measurement, and in some applications the picometer and femtometer are common. As technology improves, increasingly minute dimensions can be explored; however, disturbances such as vibrations, impurities, and the like become increasingly disruptive to sensitive operations at the nanometer level and beyond. Equipment that may be considered flat or still at the micron level, for example, can appear prohibitively rough and unsteady at the nanometer and picometer level. It is an increasing challenge to engineers to eliminate or avoid the problems associated with the inherent irregularities as dimensions diminish in size.
Vibration presents another difficulty to microscopic operations. All matter vibrates to some degree—even small thermal vibrations experienced by all matter at a temperature above absolute zero—and such vibrations can disrupt an operation that requires accuracy to the nanometer or picometer. Resonance in the supporting structures must be avoided, and to do so, the lowest mode natural frequency of the equipment used in such operations must be as high as possible. Virtually any action taken on a small operation inputs energy to the system, which can cause vibration of sensitive elements. If the input vibration forces approximate the natural frequency of a component the results due to resonance can be catastrophic.
Natural frequency increases with stiffness, but varies inversely to the size of mechanical elements; however, stiffness (or at least resistance to deflection) can be achieved by increasing size. Previous attempts at avoiding resonance have focused on increasing size to ensure that the natural frequency of the structure is higher than expected vibration levels. Also, efforts have been made to reduce the energy input and resultant vibrations. This result has limited applicability at very small dimensions where even thermal vibrations cause an appreciable energy input.